\begin{tikzpicture}
  [node/.style={circle, draw}]
  \matrix 
  [matrix of nodes,
  nodes in empty cells,
  row sep={3.5em,between origins},
  column sep={2.5em,between origins}]
  {
    &&&\node[node](n8){8};&&&\\
    &&&\node[node](n7){7};&&&\\
    &\node[node](n3){3};&&&&\node(n6)[node]{6};&\\
    \node[node](n1){1};&&\node[node](n2){2};&&\node[node](n4){4};&&\node[node](n5){5};\\
  };
  \node[right=of n8,xshift=-2.5em] (n8r) {\bcancel{$t_6$ | $x$}};
  \node[above=of n8r,yshift=-3em] {$x$ | $t_6$};
  \node[left=of n8,xshift=2.5em] {+};
  \node[right=of n7,xshift=-2.5em] (n7r) {\bcancel{$t_4$}};
  \node[left=of n7,xshift=2.5em] {/};
  \node[right=of n3,xshift=-2.5em] (n3r) {$t_2$ | $t_5$};
  \node[left=of n3,xshift=2.5em] {+};
  \node[right=of n6,xshift=-2.5em] (n6r) {$t_3$};
  \node[left=of n6,xshift=2.5em] {-};
  \node[right=of n1,xshift=-2.5em] {$a$};
  \node[right=of n2,xshift=-2.5em] {$b$};
  \node[right=of n4,xshift=-2.5em] {$c$};
  \node[right=of n5,xshift=-2.5em] {$d$};
  \draw [-] (n8) to (n7);
  \draw [-] (n7) to (n3);
  \draw [-] (n7) to (n6);
  \draw [-] (n3) to (n1);
  \draw [-] (n3) to (n2);
  \draw [-] (n6) to (n4);
  \draw [-] (n6) to (n5);
  \draw [-] (n8) [out=-150,in=90] to (n3);
\end{tikzpicture}